A hub unit for a driving wheel is arranged to support a hub and an inner race to be rotatable through a plurality of rolling elements on the inner diameter side of an outer race of a bearing.
The outer race is fixed to a knuckle for constituting a suspension system by means of a supporting flange provided on the outer peripheral surface thereof. A plurality of outer race tracks are provided on the inner peripheral surface of the outer race, and the hub and the inner race are supported on the inner diameter side of the outer race.
The hub is provided with a mounting flange for mounting the wheel in the outer end portion thereof. A first inner race track is formed in a middle part of the outer peripheral surface of the hub. An inner race is fixedly fitted on a small-diameter step portion of an inner end portion of the hub. This inner race is formed with a second inner race track. At the center of the hub, for example, in case of the hub unit for a driving wheel, a female spline for bringing a constant velocity universal joint into spline-fitting is provided.
There is also a hub unit with a sensor for detecting a speed of rotation of the wheel in order to rotatably support the wheel with respect to the suspension system and also to control an anti-lock brake system (ABS) or a traction control system (TCS).
When this hub unit is in use, a magnetic rubber encoder which is fixed to the inner race and which is magnetized to have alternately a plurality of north poles and south poles is rotated upon rotation of the wheel, and an output of the sensor disposed to face the magnetic rubber encoder is changed. Since the frequency of this output change is proportional to the speed of rotation of the wheel, an output signal of the sensor is inputted to a control unit through a harness to obtain the speed of rotation of the wheel, thereby appropriately controlling the ABS or the TCS.
Incidentally, such a hub unit as of the above-described type is, after the magnetic rubber encoder or the like is mounted on the inner race of the bearing, transported as a unitary hub unit, and the outer race thereof is fixed to a knuckle of the car body with a bolt or the like in an assembly process of the car. Then, the hub unit is mounted on the car body side.
However, it is conventionally arranged such that, in the hub unit for the driving wheel, the sensor for detecting the speed of rotation of the wheel is mounted on the side of the knuckle of the car body.
Accordingly, it is required to examine whether or not a positional relationship between the sensor for detecting the speed of rotation on the knuckle side and the magnetic rubber encoder on the hub unit side is appropriate and to adjust it. As a result, the assembling and adjusting processes become complicated.
For these reasons, there is a demand that the sensor for detecting the speed of rotation should also be mounted on the hub unit side in advance, in the same manner as the magnetic rubber encoder.
However, since the constant velocity universal joint is provided on the inner side of the hub unit in the car width direction, a space for mounting this sensor is comparatively small, so that it is difficult to mount the sensor for detecting speed of rotation on the hub unit side. Moreover, it is very troublesome to receive the harness which is extended from the sensor or to prevent interference thereof with the constant velocity universal joint.